No, no no! You should NEVER edit WordPress core files. Editing core scripts can bring down your entire site and/or open security holes for hackers to use. And there’s is simply no need for it when you are just trying to modify your theme’s menu.

It is not the general policy to delete forum posts. When a post is made and people contribute answers to an issue, that then becomes part of the community resource for others to benefit from. Deleting posts removes this added value.